Integrated circuit inductors

ABSTRACT

The invention relates to an inductor comprising a plurality of interconnected conductive segments interwoven with a substrate. The inductance of the inductor is increased through the use of coatings and films of ferromagnetic materials such as magnetic metals, alloys, and oxides. The inductor is compatible with integrated circuit manufacturing techniques and eliminates the need in many systems and circuits for large off chip inductors. A sense and measurement coil, which is fabricated on the same substrate as the inductor, provides the capability to measure the magnetic field or flux produced by the inductor. This on chip measurement capability supplies information that permits circuit engineers to design and fabricate on chip inductors to very tight tolerances.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a division of U.S. patent application Ser. No.09/821,240, filed on Mar. 29, 2001 now U.S. Pat. No. 6,357,107, which isa division of U.S. patent application Ser. No. 09/350,601, filed on Jul.9, 1999, now issued as U.S. Pat. No. 6,240,622, the specifications ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to inductors, and more particularly, it relatesto inductors used with integrated circuits.

BACKGROUND OF THE INVENTION

Inductors are used in a wide range of signal processing systems andcircuits. For example, inductors are used in communication systems,radar systems, television systems, highpass filters, tank circuits, andbutterworth filters.

As electronic signal processing systems have become more highlyintegrated and miniaturized, effectively signal processing systems on achip, system engineers have sought to eliminate the use of large,auxiliary components, such as inductors. When unable to eliminateinductors in their designs, engineers have sought ways to reduce thesize of the inductors that they do use.

Simulating inductors using active circuits, which are easilyminiaturized, is one approach to eliminating the use of actual inductorsin signal processing systems. Unfortunately, simulated inductor circuitstend to exhibit high parasitic effects, and often generate more noisethan circuits constructed using actual inductors.

Inductors are miniaturized for use in compact communication systems,such as cell phones and modems, by fabricating spiral inductors on thesame substrate as the integrated circuit to which they are coupled usingintegrated circuit manufacturing techniques. Unfortunately, spiralinductors take up a disproportionately large share of the availablesurface area on an integrated circuit substrate.

For these and other reasons there is a need for the present invention.

SUMMARY OF THE INVENTION

The above mentioned problems and other problems are addressed by thepresent invention and will be understood by one skilled in the art uponreading and studying the following specification. An integrated circuitinductor compatible with integrated circuit manufacturing techniques isdisclosed.

In one embodiment, an inductor capable of being fabricated from aplurality of conductive segments and interwoven with a substrate isdisclosed. In an alternate embodiment, a sense coil capable of measuringthe magnetic field or flux produced by an inductor comprised of aplurality of conductive segments and fabricated on the same substrate asthe inductor is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cutaway view of some embodiments of an inductor of thepresent invention.

FIG. 1B is a top view of some embodiments of the inductor of FIG. 1A.

FIG. 1C is a side view of some embodiments of the inductor of FIG. 1A.

FIG. 2 is a cross-sectional side view of some embodiments of a highlyconductive path including encapsulated magnetic material layers.

FIG. 3A is a perspective view of some embodiments of an inductor and aspiral sense inductor of the present invention.

FIG. 3B is a perspective view of some embodiments of an inductor and anonspiral sense inductor of the present invention.

FIG. 4 is a cutaway perspective view of some embodiments of a triangularcoil inductor of the present invention.

FIG. 5 is a top view of some embodiments of an inductor coupled circuitof the present invention.

FIG. 6 is diagram of a drill and a laser for perforating a substrate.

FIG. 7 is a block diagram of a computer system in which embodiments ofthe present invention can be practiced.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific preferredembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is to be understood that otherembodiments may be utilized and that logical, mechanical and electricalchanges may be made without departing from the spirit and scope of thepresent invention. The following detailed description is, therefore, notto be taken in a limiting sense, and the scope of the present inventionis defined only by the appended claims.

FIG. 1A is a cutaway view of some embodiments of inductor 100 of thepresent invention. Inductor 100 includes substrate 103, a plurality ofconductive segments 106, a plurality of conductive segments 109, andmagnetic film layers 112 and 113. The plurality of conductive segments109 interconnect the plurality of conductive segments 106 to form highlyconductive path 114 interwoven with substrate 103. Magnetic film layers112 and 113 are formed on substrate 103 in core area 115 of highlyconductive path 114.

Substrate 103 provides the structure in which highly conductive path 114that constitutes an inductive coil is interwoven. Substrate 103, in oneembodiment, is fabricated from a crystalline material. In anotherembodiment, substrate 103 is fabricated from a single element doped orundoped semiconductor material, such as silicon or germanium.Alternatively, substrate 103 is fabricated from gallium arsenide,silicon carbide, or a partially magnetic material having a crystallineor amorphous structure. Substrate 103 is not limited to a single layersubstrate. Multiple layer substrates, coated or partially coatedsubstrates, and substrates having a plurality of coated surfaces are allsuitable for use in connection with the present invention. The coatingsinclude insulators, ferromagnetic materials, and magnetic oxides.Insulators protect the inductive coil and separate the electricallyconductive inductive coil from other conductors, such as signal carryingcircuit lines. Coatings and films of ferromagnetic materials, such asmagnetic metals, alloys, and oxides, increase the inductance of theinductive coil.

Substrate 103 has a plurality of surfaces 118. The plurality of surfaces118 is not limited to oblique surfaces. In one embodiment, at least twoof the plurality of surfaces 118 are parallel. In an alternateembodiment, a first pair of parallel surfaces are substantiallyperpendicular to a second pair of surfaces. In still another embodiment,the surfaces are planarized. Since most integrated circuit manufacturingprocesses are designed to work with substrates having a pair ofrelatively flat or planarized parallel surfaces, the use of parallelsurfaces simplifies the manufacturing process for forming highlyconductive path 114 of inductor 100.

Substrate 103 has a plurality of holes, perforations, or other substratesubtending paths 121 that can be filled, plugged, partially filed,partially plugged, or lined with a conducting material. In FIG. 1A,substrate subtending paths 121 are filled by the plurality of conductingsegments 106. The shape of the perforations, holes, or other substratesubtending paths 121 is not limited to a particular shape. Circular,square, rectangular, and triangular shapes are all suitable for use inconnection with the present invention. The plurality of holes,perforations, or other substrate subtending paths 121, in oneembodiment, are substantially parallel to each other and substantiallyperpendicular to substantially parallel surfaces of the substrate.

Highly conductive path 114 is interwoven with a single layer substrateor a multilayer substrate, such as substrate 103 in combination withmagnetic film layers 112 and 113, to form an inductive element that isat least partially embedded in the substrate. If the surface of thesubstrate is coated, for example with magnetic film 112, then conductivepath 114 is located at least partially above the coating, pierces thecoated substrate, and is interlaced with the coated substrate.

Highly conductive path 114 has an inductance value and is in the shapeof a coil. The shape of each loop of the coil interlaced with thesubstrate is not limited to a particular geometric shape. For example,circular, square, rectangular, and triangular loops are suitable for usein connection with the present invention.

Highly conductive path 114, in one embodiment, intersects a plurality ofsubstantially parallel surfaces and fills a plurality of substantiallyparallel holes. Highly conductive path 114 is formed from a plurality ofinterconnected conductive segments. The conductive segments, in oneembodiment, are a pair of substantially parallel rows of conductivecolumns interconnected by a plurality of conductive segments to form aplurality of loops.

Highly conductive path 114, in one embodiment, is fabricated from ametal conductor, such as aluminum, copper, or gold or an alloy of a sucha metal conductor. Aluminum, copper, or gold, or an alloy is used tofill or partially fill the holes, perforations, or other pathssubtending the substrate to form a plurality of conductive segments.Alternatively, a conductive material may be used to plug the holes,perforations, or other paths subtending the substrate to form aplurality of conductive segments. In general, higher conductivitymaterials are preferred to lower conductivity materials. In oneembodiment, conductive path 114 is partially diffused into the substrateor partially diffused into the crystalline structure.

For a conductive path comprised of segments, each segment, in oneembodiment, is fabricated from a different conductive material. Anadvantage of interconnecting segments fabricated from differentconductive materials to form a conductive path is that the properties ofthe conductive path are easily tuned through the choice of theconductive materials. For example, the internal resistance of aconductive path is increased by selecting a material having a higherresistance for a segment than the average resistance in the rest of thepath. In an alternate embodiment, two different conductive materials areselected for fabricating a conductive path. In this embodiment,materials are selected based on their compatibility with the availableintegrated circuit manufacturing processes. For example, if it isdifficult to create a barrier layer where the conductive path piercesthe substrate, then the conductive segments that pierce the substrateare fabricated from aluminum. Similarly, if it is relatively easy tocreate a barrier layer for conductive segments that interconnect thesegments that pierce the substrate, then copper is used for thesesegments.

Highly conductive path 114 is comprised of two types of conductivesegments. The first type includes segments subtending the substrate,such as conductive segments 106. The second type includes segmentsformed on a surface of the substrate, such as conductive segments 109.The second type of segment interconnects segments of the first type toform highly conductive path 114. The mid-segment cross-sectional profile124 of the first type of segment is not limited to a particular shape.Circular, square, rectangular, and triangular are all shapes suitablefor use in connection with the present invention. The mid-segmentcross-sectional profile 127 of the second type of segment is not limitedto a particular shape. In one embodiment, the mid-segmentcross-sectional profile is rectangular. The coil that results fromforming the highly conductive path from the conductive segments andinterweaving the highly conductive path with the substrate is capable ofproducing a reinforcing magnetic field or flux in the substrate materialoccupying the core area of the coil and in any coating deposited on thesurfaces of the substrate.

FIG. 1B is a top view of FIG. 1A with magnetic film 112 formed onsubstrate 103 between conductive segments 109 and the surface ofsubstrate 103. Magnetic film 112 coats or partially coats the surface ofsubstrate 103. In one embodiment, magnetic film 112 is a magnetic oxide.In an alternate embodiment, magnetic film 112 is one or more layers of amagnetic material in a plurality of layers formed on the surface ofsubstrate 103.

Magnetic film 112 is formed on substrate 103 to increase the inductanceof highly conductive path 114. Methods of preparing magnetic film 112include evaporation, sputtering, chemical vapor deposition, laserablation, and electrochemical deposition. In one embodiment, highcoercivity gamma iron oxide films are deposited using chemical vaporpyrolysis. When deposited at above 500 degrees centigrade these filmsare magnetic gamma oxide. In an alternate embodiment, amorphous ironoxide films are prepared by the deposition of iron metal in an oxygenatmosphere (10⁻⁴ torr) by evaporation. In another alternate embodiment,an iron-oxide film is prepared by reactive sputtering of an Fe target inAr+O₂ atmosphere at a deposition rate of ten times higher than theconventional method. The resulting alpha iron oxide films are thenconverted to magnetic gamma type by reducing them in a hydrogenatmosphere.

FIG. 1C is a side view of some embodiments of the inductor of FIG. 1Aincluding substrate 103, the plurality of conductive segments 106, theplurality of conductive segments 109 and magnetic films 112 and 113.

FIG. 2 is a cross-sectional side view of some embodiments of highlyconductive path 203 including encapsulated magnetic material layers 206and 209. Encapsulated magnetic material layers 206 and 209, in oneembodiment, are a nickel iron alloy deposited on a surface of substrate212. Formed on magnetic material layer layers 206 and 209 are insulatinglayers 215 and 218 and second insulating layers 221 and 224 whichencapsulate highly conductive path 203 deposited on insulating layers215 and 218. Insulating layers 215, 218, 221 and 224, in one embodimentare formed from an insulator, such as polyimide. In an alternateembodiment, insulating layers 215, 218, 221, and 224 are an inorganicoxide, such as silicon dioxide or silicon nitride. The insulator mayalso partially line the holes, perforations, or other substratesubtending paths. The purpose of insulating layers 215 and 218, which inone embodiment are dielectrics, is to electrically isolate the surfaceconducting segments of highly conductive path 203 from magnetic materiallayers 206 and 209. The purpose of insulating layers 221 and 224 is toelectrically isolate the highly conductive path 203 from any conductinglayers deposited above the path 203 and to protect the path 203 fromphysical damage.

The field created by the conductive path is substantially parallel tothe planarized surface and penetrates the coating. In one embodiment,the conductive path is operable for creating a magnetic field within thecoating, but not above the coating. In an alternate embodiment, theconductive path is operable for creating a reinforcing magnetic fieldwithin the film and within the substrate.

FIG. 3A and FIG. 3B are perspective views of some embodiments ofinductor 301 and sense inductors 304 and 307 of the present invention.In one embodiment, sense inductor 304 is a spiral coil and senseinductor 307 is a test inductor or sense coil embedded in the substrate.Sense inductors 304 and 307 are capable of detecting and measuringreinforcing magnetic field or flux 309 generated by inductor 301, and ofassisting in the calibration of inductor 301. In one embodiment, senseinductor 304 is fabricated on one of the surfaces substantiallyperpendicular to the surfaces of the substrate having the conductingsegments, so magnetic field or flux 309 generated by inductor 301 issubstantially perpendicular to sense inductor 304. Detachable test leads310 and 313 in FIG. 3A and detachable test leads 316 and 319 in FIG. 3Bare capable of coupling sense inductors 304 and 307 to sense ormeasurement circuits. When coupled to sense or measurement circuits,sense inductors 304 and 307 are decoupled from the sense or measurementcircuits by severing test leads 310, 313, 316, and 319. In oneembodiment, test leads 310, 313, 316, and 316 are severed using a laser.

In accordance with the present invention, a current flows in inductor301 and generates magnetic field or flux 309. Magnetic field or flux 309passes through sense inductor 304 or sense inductor 307 and induces acurrent in spiral sense inductor 304 or sense inductor 307. The inducedcurrent can be detected, measured and used to deduce the inductance ofinductor 301.

FIG. 4 is a cutaway perspective view of some embodiments of triangularcoil inductor 400 of the present invention. Triangular coil inductor 400comprises substrate 403 and triangular coil 406. An advantage oftriangular coil inductor 400 is that it saves at least a process stepover the previously described coil inductor. Triangular coil inductor400 only requires the construction of three segments for each coil ofinductor 400, where the previously described inductor required theconstruction of four segments for each coil of the inductor.

FIG. 5 is a top view of some embodiments of an inductor coupled circuit500 of the present invention. Inductor coupled circuit 500 comprisessubstrate 503, coating 506, coil 509, and circuit or memory cells 512.Coil 509 comprises a conductive path located at least partially abovecoating 506 and coupled to circuit or memory cells 512. Coil 509 piercessubstrate 503, is interlaced with substrate 503, and produces a magneticfield in coating 506. In an alternate embodiment, coil 509 produces amagnetic field in coating 506, but not above coating 506. In oneembodiment, substrate 503 is perforated with a plurality ofsubstantially parallel perforations and is partially magnetic. In analternate embodiment, substrate 503 is a substrate as described above inconnection with FIG. 1. In another alternate embodiment, coating 506 isa magnetic film as described above in connection with FIG. 1. In anotheralternate embodiment, coil 509, is a highly conductive path as describedin connection with FIG. 1.

FIG. 6 is a diagram of a drill 603 and a laser 606 for perforating asubstrate 609. Substrate 609 has holes, perforations, or other substrate609 subtending paths. In preparing substrate 609, in one embodiment, adiamond tipped carbide drill is used bore holes or create perforationsin substrate 609. In an alternate embodiment, laser 606 is used to borea plurality of holes in substrate 609. In a preferred embodiment, holes,perforations, or other substrate 609 subtending paths are fabricatedusing a dry etching process.

FIG. 7 is a block diagram of a system level embodiment of the presentinvention. System 700 comprises processor 705 and memory device 710,which includes memory circuits and cells, electronic circuits,electronic devices, and power supply circuits coupled to inductors ofone or more of the types described above in conjunction with FIGS.1A-5.Memory device 710 comprises memory array 715, address circuitry 720, andread circuitry 730, and is coupled to processor 705 by address bus 735,data bus 740, and control bus 745. Processor 705, through address bus735, data bus 740, and control bus 745 communicates with memory device710. In a read operation initiated by processor 705, addressinformation, data information, and control information are provided tomemory device 710 through busses 735, 740, and 745. This information isdecoded by addressing circuitry 720, including a row decoder and acolumn decoder, and read circuitry 730. Successful completion of theread operation results in information from memory array 715 beingcommunicated to processor 705 over data bus 740.

CONCLUSION

Embodiments of inductors and methods of fabricating inductors suitablefor use with integrated circuits have been described. In one embodiment,an inductor having a highly conductive path fabricated from a pluralityof conductive segments, and including coatings and films offerromagnetic materials, such as magnetic metals, alloys, and oxides hasbeen described. In another embodiment, an inductor capable of beingfabricated from a plurality of conductors having different resistanceshas been described. In an alternative embodiment, an integrated test orcalibration coil capable of being fabricated on the same substrate as aninductor and capable of facilitating the measurement of the magneticfield or flux generated by the inductor and capable of facilitating thecalibration the inductor has been described.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiment shown. This application isintended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

1. An inductor comprising: a substrate having a plurality of holes and aplurality of surfaces; a conductive material having a conductivity of atleast copper and filling at least three of the plurality of holes toform a plurality of conductive segments; and a plurality of conductiveinterconnects formed on at least one of the plurality of surfaces andcoupling to the plurality of conductive segments to form a continuousconductive coil.
 2. The inductor of claim 1, wherein the conductivematerial includes copper or gold.
 3. The inductor of claim 1, whereinthe continuous conductive coil has a triangular cross-section.
 4. Theinductor of claim 1, wherein the substrate includes one or more magneticfilms at least partially surrounded by the coil.
 5. The inductor ofclaim 4, wherein the one or more magnetic films comprises a magneticoxide.
 6. The inductor of claim 1, further including at least two leadsconnected to the coil.
 7. The inductor of claim 6, further including acircuit connected to the at least two leads.
 8. An inductor comprising:a substrate having a plurality of holes connecting opposing substratesurfaces; a conductive material having a conductivity equal to orgreater than that of copper filling the plurality of holes to form aplurality of conductive segments; and a plurality of conductiveinterconnects coupled to the plurality of conductive segments to form acontinuous conductive coil that surrounds the opposing substratesurfaces.
 9. The inductor of claim 8, further including a magnetic filmformed between one of the substrate opposing surfaces and the pluralityof conductive interconnects.
 10. The inductor of claim 9, wherein themagnetic film comprises a magnetic oxide.
 11. The inductor of claim 8,further including two or more leads connected to the coil.
 12. Theinductor of claim 11, further including a circuit connected to the twoor more leads.
 13. The inductor of claim 9, further including aninsulator layer covering the magnetic film.
 14. The inductor of claim 8,wherein the coil has a rectangular cross-section.
 15. The inductoraccording to claim 8, wherein the conductive material has a conductivityequal to or greater than that of copper.
 16. The inductor of claim 15,wherein the conductive material comprises copper or gold.
 17. Aninductor comprising: a semiconductor substrate having a plurality ofthrough holes and a plurality of layers: copper filling the throughholes to form a plurality of copper segments; and a plurality ofconductive interconnects coupled to the plurality of copper segments toform a continuous conductive coil surrounding the substrate and at leastone of the plurality of layers.
 18. The inductor of claim 17, whereinthe plurality of layers includes a magnetic film.
 19. The inductor ofclaim 18, wherein the plurality of layers includes an insulating layercovering the magnetic film.
 20. The inductor of claim 18, wherein themagnetic film is surrounded by the conductive coil.
 21. The inductor ofclaim 17, wherein the conductive interconnects are copper.
 22. Aninductor comprising: a substrate having a plurality of holes connectingtwo of a plurality of substrate surfaces; one or more layers of magneticmaterial formed on at least one of the substrate surfaces; a conductivematerial filling the plurality of holes to form a correspondingplurality of conductive segments, the conductive material having aconductivity equal to or greater than that of copper; and a plurality ofconductive interconnects coupled to the plurality of conductive segmentsto form a continuous conductive coil that surrounds the substratesurfaces and at least one of the one or more layers.
 23. The inductor ofclaim 22, further including at least two conductive leads connected tothe coil.
 24. The inductor of claim 23, further including a circuitconnected to the at least two conductive leads.
 25. The inductor ofclaim 24, wherein the circuit includes memory cells.
 26. The inductor ofclaim 22, wherein the conductive material is copper.
 27. The inductor ofclaim 22, wherein the conductive material is gold.